A combine harvester is a machine that is used to harvest grain crops. The objective is to complete several processes, which traditionally were distinct, in one pass of the machine over a particular part of the field. Among the crops that may be harvested with a combine are wheat, oats, rye, barley, corn, soybeans, and flax or linseed. The waste (e.g., straw) left behind on the field includes the remaining dried stems and leaves of the crop having limited nutrients which may be, for example, chopped and spread on the field or baled for feed and bedding for livestock.
The cut crop may be picked up and fed into the threshing and separating mechanism of the combine, typically consisting of a rotating threshing drum to which grooved steel bars may be bolted. These bars thresh or separate the grains and chaff from the straw through the action of the drum against the concaves, i.e., shaped “half drum,” that may also be fitted with steel bars and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too big or long, is carried through to the outlet. Typically, the drum speed may be variably adjustable and the distance between the drum and concave may be finely adjustable laterally and together, to achieve optimum separation and output.
In an axial flow combine, the harvested crop is threshed and separated as it is conveyed between a longitudinally arranged rotor and the inner surface of an associated chamber comprising threshing and separating concaves. The crop material spirals and is conveyed along a helical path along the inner surface of the chamber until it reaches the end thereof for expulsion out of the rear of the combine. In other embodiments, the combine may include a threshing design that is positioned transversely in a combine
Even though the crop flow spirals and follows a helical path as the crop is pulled through the rotor, historically and up until somewhat recently, all of the rub bars of the concave were straight and perpendicular with the side sheet (side walls) of the weldment of the concave frame. More recently, concaves have incorporated angled cross or rub bars so that the bars are more perpendicular to the crop flow to increase the likely expulsion of grain through the concave, and to increase the aggressiveness of the concave on the crop. These angle rub bars extend fully across the width of the concave.
Conventional concaves are of a welded construction. For example, a typical welded construction of a concave may include welded rub bars that may form a helical shape relative to the parallel side bars (wires) and frame side walls and are of various lengths depending on their position on the concave. The rub bars extend fully from a side or edge of the concave to another side or edge. As such, these conventional welded concaves have multiple part numbers involved and there is a detailed and intricate weld fixturing required to physically position these bars appropriately in a helical fashion. Conventional welded construction used to produce the helical shape is very time and cost intensive.
As can be appreciated by one of ordinary skill in the art, there is a tremendous amount of weld joints on each part and the weld process introduces heat and distortion on the concave. The concave is somewhat of a precision part typically requiring manufacturing and installation precision within millimeters of the radius, i.e. an internal radius of these parts. Welding may end up distorting the part and causing the part to be out of desired manufacturing tolerances.
What is needed is an improved helical bar concave and method of making a helical bar concave that solve one or more of the above problems with conventional concaves.